Interior noise control through tuned loudspeaker absorption

In this work we describe the development and application of an interior noise control approach based on active loudspeaker tuning for sound absorption. Loudspeakers are tuned to minimize global sound pressure at specific acoustic modes through diaphragm velocity feedback. An experimental model of the acoustic space used for controller design is obtained through system identification. H2 optimal controllers are designed to minimize a performance microphone output by feeding back the tuned loudspeaker diaphragm velocity. By sensing speaker velocity rather than far-field sound pressure, the loudspeaker is actively tuned to minimize reflected sound at specific acoustic modes and therefore reduce the global pressure field. Experimental results, obtained from an acoustic enclosure modeled after a rocket fairing, are used to demonstrate the effectiveness of the tuned loudspeaker at global attenuation. Details of the design procedure and experimental applications are discussed.